Ben may be in the throes of terminal cancer, but his wife, Rita, is determined to know what he thinks about redoing their living room.

“I’m dying,” he groans.

“Yes, I know,” she replies. “Try to be positive.”

Nicky Silver’s “The Lyons” — which opened on Broadway last night after a hit run at the Vineyard — is packed with such sweet nothings. When you hear them delivered by pros like Dick Latessa and Linda Lavin, it’s comedy nirvana.

Lavin is particularly fabulous in a juicy role from which she squeezes every drop. It’s never less than a treat to watch this expert in action, starting with the way Rita fires off put-downs while idly flipping through a magazine.

Ben himself shows no sign of mellowing, spitting out profanities to which his wife responds with cool contempt. You get the feeling this has been going on for a while, and only death could end it.

She’s a high-strung recovering alcoholic who’s never been happy — her one meaningful memory turns out to be from “Kramer vs. Kramer.”

He’s a tweedy, needy writer full of resentment. “I refuse to relive the Hindenburg of my childhood,” he spits out after Rita asks if he’d like to move back with her.

While Ben hates his son’s homosexuality, Rita dislikes both children equally.

Silver (“Pterodactyls,” “Raised in Captivity”) doesn’t break new ground, but his vehicle is satisfyingly mean and funny, and director Mark Brokaw steers it adroitly.

The playwright’s also smart enough to know that a bitchfest only goes so far.

The show takes a left turn in the second half, when we discover the full extent of Curtis’ misery, but also Rita’s obstinate willpower. She finally takes charge after decades stuck with an obnoxious husband and selfish, callous offspring, and Lavin does her full justice.

This makes the story’s twists less surprising — the show reads broader at the Cort than it did off-Broadway — but at least Rita’s gained in complexity. She’s still a controlling handful, but also reveals early flashes of unhappiness, making her later decisions easier to understand.

When Rita finally tells her kids what’s what, you want to stand up and cheer — for the character, and for the brilliant actress bringing her to life.